Amidon Split Core for rounds cables. 43 Material, Diameter 0.5" ID: 0.528 OD: 1.142 HT: 1.28 Typical Impedance 25MHz = 156, 100MHz = 250, 250MHz = 305. Use these wherever you have an interference problem or you even think you may have one. Clamp these on cables and tape them in place if needed. Use these coming and going; If an appliance such as a TV, radio, HiFi, or fire extinguisher is being interfered with then put one or more of these on the power cord, antenna, i/o cable to see if there is a reduction in interference. If one helps two will help more; stack them on.View Spec Sheet